Derivative Financial Instruments - Narrative (Details) (USD $)	12 Months Ended										12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 01, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Jun. 30, 2013 Cash Flow Hedging [Member]	Jun. 30, 2012 Cash Flow Hedging [Member]	Jun. 30, 2011 Cash Flow Hedging [Member]	Jun. 30, 2013 Deposits Held At CommodityTrading Accounts [Member]	Jun. 30, 2012 Deposits Held At CommodityTrading Accounts [Member]
Derivative [Line Items]
Derivative Instruments, Percentage Designated As Cash Flow Hedges	89.00%
Loss on Cash Flow Hedge Ineffectiveness	$ 400,000
Losses recognized in OCI											(7,921,000)	0	0
Restricted cash	8,084,000	3,751,000	3,599,000		129,000	1,612,000	1,774,000	1,813,000	628,000	460,000				8,100,000	1,600,000
Notional Amount of Interest Rate Derivatives	10,000,000			10,000,000
Derivative, Fixed Interest Rate	0.48%
Net losses to be reclassified into earnings within the next twelve months	$ 6,800,000
Derivative Instruments, Percentage Excluded from Effectiveness Testing	11.00%